basically is want to make a circuit that takes 0-5v input and converts it in and corresponding output current of 4-20mA using opamp , i have seen reference circuit from this pdf https://www.analog.com/media/en/technical-documentation/technical-articles/D61_EN-Convert.pdf
but it has converted from 1-5v to 4-20mA current source
but i want to make a circuit that converts 0-5 to 4-20mA current source
Electrical – circuit for converting in 0-5v to 4-20mA current source
4-20mamosfetoperational-amplifier
Related Solutions
As Feilthry pointed out my problem might be commom-mode chokes L4 and L5. So, I tried replacing them with new ones (new part is RL822-3R3K-RC), then my problem was solved. It now can drive 4-20mA current consistantly on load resister at 0-500ohms.
Sorry that I can't find a datasheet for KV03405 to compare parameters. I think it's because the new chokes got a highter Self Resonant frequency than last one.
"Triggered" suggests something that will suddenly switch from one state to another. That's probably not the right word.
As this is an analog circuit we can expect M2 to turn on gradually under certain conditions. "Turned on" would be a better term.
Since the feedback is taken after M2 it means that the output of the op-amp will go as high as it needs to to turn on M2 enough to get the feedback voltage to match the input voltage.
simulate this circuit – Schematic created using CircuitLab
Figure 1. Running the CircuitLab DC Solver for 4 V in results in 8 V at NODE1.
Best Answer
You can always just use your reference circuit (1-5V input) and convert your 0-5V input to 1-5V with two resistors:
simulate this circuit – Schematic created using CircuitLab
If you don't have a +5V rail, you can create an equivalent from any higher rail with a pair of resistors and a little math:
simulate this circuit